1. Field of the Invention
The present invention relates to an adjusting mechanism for installation of a plate-like member such as a reflector used in an optical scanner.
2. Description of the Related Art
The optical scanner used in an image forming apparatus such as a copying machine or printer is generally arranged so that a laser beam emitted from a laser source and containing image information is appropriately focused, then enters deflector means such as a polygon mirror and the laser beam thus deflected irradiates and scans an image carrier as an object to be scanned, for example, a photosensitive drum and forms an electrostatic latent image on this image carrier. This electrostatic latent image is developed with toner to form a toner image, which is then transferred to a transfer medium such as recording paper to form a visible image thereon. As color image forming apparatus, for example, color copying machine or color printer, the image forming apparatus of tandem type has been widely used. In the image forming apparatus of this type, a plurality of image carriers such as photosensitive drums are arranged side by side so that electrostatic latent images may be formed on the respective image carriers as the laser beams containing the image data colored in yellow (Y), magenta (M), cyan (C) and black (BK), respectively, irradiate and scan respective said image carriers. These electrostatic latent images are developed by respective particular kinds of toner to form respective toner images which are then successively transferred to the transfer medium such as recording paper travelling in the direction of the image carriers' side by side arrangement to form color images thereon.
Demand for pluralization of the light beam for scanning and the scanning unit has increased as the high-speed copying machine and the printer have come widely in use. Additionally, in order to ensure the formed image to be distinct, optical characteristics of these plural scanning lights beams as well as the scanning characteristics of these plural scanning units must meet the predetermined requirements and the characteristics of these plural units must be uniform. To ensure the required optical characteristics and the scanning characteristics, installation precision of the optical members constituting the optical scanner must be sufficiently high to achieve the proper operative association one with another. Particularly, even a slight error in the reflecting direction of the reflector or variation in the installed state will deteriorate the optical characteristics as well as the scanning characteristics. To avoid such problems, the reflecting direction of the reflector should be adjusted with high precision.
The adjusting mechanism for installation of the reflector is well known, in which the spacer as thin as possible, for example, a mica plate is disposed between the reflector and the bracket on which the reflector is mounted and thereby said reflector is adjustably tilted. The mirror adjusting mechanism shown by FIG. 28 in the accompanying drawings is well known from Japanese Patent Application Disclosure Gazette No. 1999-281876. This mirror adjusting mechanism of prior art is arranged as follows: The reflector 1 is pivotally supported at its lower end by the mirror supporting member 2 while there is provided the spring member 3 fixed to said mirror supporting member 2 so as to bias the upper end of the reflector 1 from its rear side. The mirror adjusting member 4 kept in contact with the front surface of the reflector 1 at its upper end is moved to adjust the reflector 1 at a desired angle and thereafter said mirror adjusting member 4 is fixed by the set screw 5 to maintain the reflector 1 tilted at this angle.
These conventional adjusting mechanisms as have been described above are inevitably accompanied with the problems as follow. In the case of the mechanism adapted to dispose the spacer between the reflector and the bracket to tilt the reflector, it is certainly possible to adjust a tilt of the reflector omni-directionally. However, the extremely thin spacer makes operation of adjustment troublesome. In addition, a clamping force of the set screw used to fix the reflector is not uniform and consequently it is sometimes impossible to make the reflector face in the desired direction. In other words, no quantitative adjustment is impossible and the adjusting effect largely depends on working accuracy of the components such as the spacer, the reflector and the brackets.
The mirror adjusting mechanism described in said Japanese Patent Application Disclosure Gazette No. 1999-281876 is adapted to adjust a tilt angle of the reflector only in a single direction and not suitable for adjustment of the reflector incorporated into the optical scanner or the like.